This invention relates to a heat storage type air conditioner which has a heat storage tank containing a heat storing medium, and contributes to suppression of the electric power consumption during the daytime, and to make the periodic electric power consumption uniform in a day.
FIG. 14 is a refrigerant piping circuit diagram showing the arrangement of a conventional heat storage type air conditioner disclosed, for instance, by Japanese Patent Application (OPI) No. 33573/1990 (the term "OPI" as used herein means an "unexamined application"). The air conditioner comprises: a main refrigerant circuit 6 including a compressor 1, a condenser 2, a first pressure reducing mechanism 3, and an evaporator 4, which are connected to one another in the stated order; a heat storage tank 8 containing a heat storing medium 7; a cold storing heat exchanger 9a for performing heat exchange between the heat storing medium 7 in the heat storage tank and the refrigerant; a first bypass circuit 10 allowing the refrigerant to move through the heat exchanger 9a between a liquid pipe 5a provided between the condenser 2 and the first pressure reducing mechanism 3 and a gas pipe 5b; a second pressure reducing mechanism 11 connected to a liquid pipe 10a of the first bypass circuit 10; a second bypass circuit 12 connected in parallel to a gas pipe 10b of the first bypass circuit 10; a refrigerant gas pump 13 connected to the second bypass circuit 12 and adapted to circulate the refrigerant to perform heat exchange between the refrigerant and the heat storing medium 7 contained in the heat storage tank 8; and control means (opening and closing means) 14 for controlling the flow of refrigerant to the second bypassing circuit 12.
The operation of the conventional air conditioner thus organized will be described. The devices 1 through 4 are connected through a refrigerant pipe 5 to one another to allow the flow and circulation of refrigerant, to form the main refrigerant circuit 6, which is adapted to give to the air in the room with the aid of the evaporator 4 the cold which the condenser 2 has obtained from the air outside the room by heat exchange.
On the other hand, the conventional air conditioner includes the heat storage tank 8 containing the heat storing medium 7 which is able to store heat. And the cold storing heat exchanger 9a is provided in the heat storage tank, to perform heat exchange between the heat storing medium 7 in the heat storage tank 8 and the refrigerant.
In an ordinary cooling operation using the compressor (hereinafter referred to as "a general cooling operation", when applicable), the second pressure reducing mechanism 11 is kept closed, and the refrigerant circulates only in the main refrigerant circuit 6. That is, the gas-like refrigerant high in temperature and high in pressure discharged from the compressor circulates as follows: First, the refrigerant is condensed by the condenser 2, and then subjected to adiabatic expansion by the first pressure reducing mechanism 3, as a result of which it is converted into a two-phase (gas and liquid) fluid low in temperature. The fluid flows into the evaporator 4, where it takes heat from its surroundings to cool the latter, and it is evaporated and gasified, to return to the compressor 1.
In a cold storing operation which is performed for storage of cold during night time when the electric power load is small, the first pressure reducing mechanism 3 is kept closed. That is, the gas-like refrigerant discharged from the compressor 1 is condensed by the condenser 2 into a liquid refrigerant. The liquid refrigerant flows to the first bypass circuit 10, and is then subjected to adiabatic expansion by the second pressure reducing mechanism 11, and thereafter evaporated and gasified by the cold storing heat exchanger 9a, so that the cold is stored in the heat storing medium 7 in the heat storage tank 8.
In a cooling operation using the stored cold, in which the cold stored in the heat storage tank 8 during night time is used, for instance, during day time (hereinafter referred to as "a cold radiating operation", when applicable), the refrigerant is processed as follows: That is, when, with the compressor 1 stopped, the refrigerant gas pump 13 is operated, the gas refrigerant at low temperature and at low pressure is pressurized by the pump 13, so that it is moved through the gas pipe 10b of the first bypass circuit 10 to the cold storing heat exchanger 9a, where it gives its heat to the heat storing medium 7, and then condensed and liquified. The refrigerant thus condensed and liquified is subjected to adiabatic expansion by the second pressure reducing mechanism 11, so that it is converted into a two-phase (gas and liquid) fluid. The two-phase fluid flows into the evaporator 4, where it takes heat from its surroundings thereby to cool the latter, and it is evaporated and gasified, to return to the refrigerant gas pump 13.
With the conventional air conditioner, the cold radiating operation and the general cooling operation using the compressor 1 can be performed at the same time. More specifically, the air conditioner may be operated with both the compressor 1 and the pump 13 activated. The refrigerant condensed by the condenser 2 in the main refrigerant circuit 6, and the refrigerant condensed by the heat exchanger 9a in the first bypass circuit 10 meet each other at the liquid pipe 5a of the main refrigerant circuit 6, and both of them are evaporated at the evaporator 4, thus cooling the surrounding.
The simultaneous operation of the compressor 1 and the refrigerant gas pump 3; that is, to perform the general cooling operation and the cold radiating operation at the same time is effective in decreasing the load to the demand for electric power during day time. However, the above-described method, in which the refrigerants condensed by the condenser 2 and the cold storing heat exchanger 9a are met with each other, and evaporated by one and the same evaporator 4, suffers from the following difficulty: That is, depending on variations of environmental conditions such as the temperature of the air in the room and the temperature of the air outside the room, and on variations in load of the cold storing heat exchanger 9a due to variations in temperature of the heat storing medium, the general cooling operation and the cold radiating operation may be unbalanced in the quantities of refrigerant and refrigerating machine oil required therefor. In this case, the air conditioner may operate unsatisfactorily, and may be lowered in cooling capacity. In addition, when the quantity of refrigerant becomes smaller or larger than required as was described above, high pressure may be induced in each of the circuits, or liquid may flow back to the compressor. Furthermore, the refrigerating machine oil may become short, so that the compressor's bearings are seized. That is, the components forming the refrigerant circuit may be damaged directly.
The above-described difficulties may be eliminated by employing a method in which the operating capacities of the compressor and the refrigerant gas pump are adjusted to control the flow rate ratio of the condensed refrigerant in the circuit for the general cooling and heating operation to that in the circuit for the cold radiating operation (the bypass circuit). However, the method is disadvantageous in the following points: That is, the control method is intricate, and accordingly it is necessary to employ control devices relatively high in cost, and in many cases it is necessary to connect a number of transmission lines to the control devices, and in addition it is required to provide mechanisms (such as inverters) for adjusting the capacities of the compressor and the refrigerant gas pump. Thus, the method is not practical in use.
The quantities of refrigerant required for the cold storing operation, the general cooling operation, and the cold radiating operation are different from one another. The quantities of refrigerant required for the cold storing operation and the general cooling operation are relatively small, whereas the quantity of refrigerant for the cold radiating operation is relatively large. Hence, in the cold storing operation, the larger part of the refrigerant in the whole circuit is surplus; and when the current operation mode is switched over to an operation mode in which only the cold radiating operation is carried out, or a combined-operation mode in which the cold radiating operation and the general cooling operation are carried out, a large quantify of refrigerant is required. Therefore, if it is intended to adjust the correct quantity of refrigerant to a correct value for any one of the operation modes, then it is necessary to provide in the circuit a device which is able to temporarily collect the refrigerant and supply it when necessary. However, in the conventional air conditioner, no means for adjusting the quantity of refrigerant suitably according to a given operation mode is provided in the circuit. In view of this adjustment of the quantity of refrigerant, it is rather difficult to put the conventional air conditioner in practical use.
FIG. 15 shows the arrangement of an air conditioner using a heat accumulator effective in storing heat, disclosed by Japanese Patent Application (OPI) No. 52563/1986, which is so designed as to perform a defrosting operation during a heating operation. The air condition comprises a heat pump circuit f including a compressor a, a 4-way valve b, an outside heat exchanger c, a pressure reducing mechanism d, and an inside heat exchanger e, which are connected to one another. In the air conditioner, the discharge side of the compressor a is connected through a defrosting first bypass circuit g to the liquid pipe of the heat pump circuit f, and the liquid pipe of the heat pump circuit f is connected through a second bypass circuit h to the suction side of the compressor a. In addition, a heat accumulator i is provided over both the gas pipe of the heat pump circuit f and the second bypass circuit h, and first and second control valves j and k are connected to the first bypass circuit g and the liquid pipe of the heat pump circuit f, respectively. In an ordinary heating operation, with the first control valve j closed and with the second control valve k opened, the refrigerant is allowed to flow as indicated by the solid arrows so that while the heating operation is being performed, the heat of the high-pressure gas discharged from the compressor a is stored in the heat accumulator i. And, in a defrosting operation, with the first control valve j opened, the gas discharged from the compressor a is sent to the outside heat exchanger c as indicated by the broken arrows to defrost it, and with the second control valve k closed a part of the gas discharged from the compressor is circulated from the inside heat exchanger through the pressure reducing mechanism d to the heat accumulator i, so that it is subjected to heat exchange at the heat accumulator i. Thus, the defrosting operation is carried out while the heating operation is being performed.
The conventional air condition is designed as described above. That is, in the case where the general cooling circuit and the cold radiating circuit are operated in a parallel mode, the refrigerants which are excessively cooled and decreased in pressure in those circuits are met with each other at the evaporator, and therefore the quantities of refrigerant in the circuits and the quantity of refrigerating machine oil are changed depending on variations in environmental condition and on variations of load on the side of the cold storing heat exchanger, as a result of which sometimes it becomes difficult to continue the operations with the circuits. This difficulty may occur in the case, too, where the conventional air conditioner performs the heating operation or the heat storing operation with the refrigerant circulating direction reversed in the refrigerant circuit.
Whenever any one of the operation modes (the cooling operation, the heating operation, the cold storing operation and the heat storing operation) is selected, the quantity of refrigerant required for the operation mode thus selected may be different from the quantity of refrigerant in the corresponding circuit. However, heretofore no means including a control unit for adjusting the quantity of refrigerant in the circuit to the correct value is provided for the conventional air conditioner, and therefore, whenever the operation mode is switched, the quantity of refrigerant in the corresponding circuit may be larger or smaller than required. This difficulty adversely affects particularly the cold storing operation; that is, it may become difficult to continue the cold storing operation. Thus, it is rather difficult to put the conventional air condition in practical use.
In the conventional air conditioner, the defrosting operation is of so-called "hot gas defrosting system" that the gas discharged from the compressor a is sent to the outside heat exchanger c, and is then returned directly (without passing through the pressure reducing mechanism) to the compressor a. Therefore, the amount of heat radiation at the outside heat exchanger c is small with respect to the ability of the compressor a; that is, the air conditioner is low in defrosting efficiency.
Furthermore, if, in the above-described conventional air conditioner, the pressure reducing mechanism d is slightly throttled to take heat from the heat accumulator i during the defrosting operation, then almost all the refrigerant flows from the bypass circuit g to the outside heat exchanger c, but not to the inside heat exchanger e, and therefore it is impossible to increase the heating capacity of the inside heat exchanger.
On the other hand, during the heating operation, the gas discharged from the compressor radiates its heat at the heat accumulator i at all times, and accordingly the heating capacity of the inside heat exchanger e is decreased. Particularly when the temperature of the air outside is low and the room heating load is great, the heating capacity of the inside heat exchanger e is unavoidably decreased.
As is apparent from the above description, the conventional air conditioner cannot sufficiently achieve its one object of performing the defrosting operation while air-conditioning the room smoothly and effectively.